Certain anemone species, such as Aiptasia pallida, A. pulchella, A. insignis, Anemonia majano and Boloceroides mcmurrichi are nuisance pests in reef aquariums. Aiptasia species are the most common anemones and generally referred to as glass anemones. These species are very widespread and thrive in shallow, nutrient rich sea water, in tropical and subtropical regions. They are easily and inadvertently introduced into reef aquariums with “live rocks” and corals.
Aiptasia anemones are typically light brown in color, have one leg, usually less than 2 inches tall, an oral disc of about ½ inch diameter with a central mouth, and long tapered tentacles. In favorable conditions these anemones may grow to 4 inches tall or more. Although Aiptasia are photosynthetic species, in absence of light or in shaded areas they consume organic detritus such as plankton and suspended organic particles in order to reach their energetic demands.
Aiptasia anemones are members of the phylum Cnidaria, and, like other Cnidarians, have cells called cnodocytes, otherwise known as canidae cells or nematocysts which contain a stinging mechanism. These cnodocytes release a toxin that is harmful to many of both the invertebrates and corals kept in reef aquariums. Consequently, corals coming into contact with Aiptasia generally recede and show signs of distress, and may die.
Aiptasia anemones are notoriously difficult to eliminate. They attach themselves to a hard substrate, usually in a crevice thereof, which allows them to quickly withdraw when danger approaches. They have remarkable powers of regeneration so cutting, grinding or smashing these anemones may propagate rather than eliminate them. In addition, they rapidly reproduce asexually through the process known as pedal laceration, which occurs when residual tissue lobes are left behind as the anemone wanders around. These residual lobes quickly develop into new anemones. Furthermore, under adequate conditions, Aiptasia anemones can reproduce sexually by releasing thousands of fertilized oocysts to the water. Because Aiptasia anemones reproduce quickly, and have extreme regenerating abilities, it is important to eliminate them before they overrun an aquarium in a short period of time.
Majano anemones (Anemonia majano) are the prettier of the pest anemones found in reef aquariums. Majano anemone specimens may be green, red, and even a striking yellow. They are not nearly as prolific as Aiptasia, and are somewhat attractive, and therefore are generally less of a nuisance to the reef aquarium hobbyist. They can easily be distinguished from Aiptasia because they have bulbous tips on the ends of their tentacles. However, like Aiptasia, they have a potent sting and may be harmful to other sessile invertebrates in the aquarium.
Boloceroides mcmurrichi, or the Swimming anemone, is another pest anemone similar to Aiptasia species. This tan anemone has a short leg and long robust tentacles that may be banded. The oral disk thereof is small and the mouth is white. The swimming anemones reproduce by the same asexual mechanism as Aiptasia and by regeneration of detached tentacles. They are photosynthetic creatures, harboring zooxanthellae algae, but can thrive in shaded nutrient rich areas.
There are two basic approaches that are currently used for controlling the pest anemone population in aquaria. One is by natural predation and the other is a chemical approach.
A newly found predator and perhaps the one with the best potential for controlling Aiptasia is Berghia verrucicornis. This nudibranch was identified in a scientific article by Carrol & Kempf (1). Berghia verrucicornis along with most nudibranchs are diet specific. Starter cultures have been exchanged and several aquaculture facilities in the US produce and provide these commercially. However, there are only a limited number of such cultures available and the specimens that can be found are generally too small be put in to a large system and expected to live. Indeed, amongst other dangers, they might fall prey to their very quarry (2). In addition, Aiptasia-eating Nudibranch are expensive and difficult to acquire; and they will eat nothing else other than Aiptasia so that once there are no Aiptasia left in an ecosystem, or so few the nudibranch has trouble finding them, it will starve to death (3-8). Furthermore, a lengthy period may be required to completely eradiate Aiptasia by employing the nudibranch (7). Other natural predators of Aiptasia species and Boloceroides mcmurrichi are the Copperband butterfly fish (Chelmon rostratus) and the Peppermint shrimp (Lysmata wurdemanni) but there is an inherent danger of these predators eating other, desired tank residents instead of or in addition to the pest anemones.
Chemical approaches to eliminating Aiptasia are more widely used. Generally these involve taking a chemical solution of minerals and placing a large dose over the oral disk. One popular method employs an aqueous suspension of calcium hydroxide (lime, kalkwasser) which may be dispensed via a syringe onto or near the Aiptasia. The popularity of the approach is partly due to the fact that many reef aquarium hobbyists already have calcium hydroxide on hand for use to maintain/supplement calcium and alkalinity. Additionally, excess calcium hydroxide merely contributes to the calcium concentration in the aquarium, whereas other targeted poisons may be harmful to desired organisms in the aquarium and cannot be left to drift in the water.
Mixed success has been reported with the chemical approach however (4-5, 9), depending upon the chemical used and the method of employing the chemical.
U.S. Pat. No. 7,179,478 and U.S. Patent Application Publication No. 2007/0119788, both to Gatto, which are incorporated by reference for all purposes as if fully set forth herein, disclose a method of killing Aiptasia and Majano anemones in aquariums, by filling a dispenser with an anemone killing mixture comprising purified water and effective amounts of calcium hydroxide and a non-iodized salt, placing a tip of the filled dispenser near the oral disk of an anemone and dispensing a small amount of the mixture. The calcium hydroxide reacts with the anemone tissues to destroy the anemone. Such a killing mixture, is available commercially under the name Joe's Juice (10). The effectiveness of the mixture is questionable, since, when threatened, the Aiptasia often shut or disappear into crevices and getting them to stay open and ingest such mixtures is difficult. It is particularly difficult to inject such mixtures near the mouth of the anemone and to visibly follow where the mixture went to. Consequently, applying the mixture may be quite tedious if many anemones need to be eradicated. In addition, the mixture is highly caustic and some care should be given to handling it for the user's safety and for fear of collateral damage to sensitive cohabitants of aquariums, and large doses may affect the pH of the water.
There is thus a need for an improved composition and method of treatment for controlling anemone pests.